What's Hot: Potentially doubles the smartphone's runtime, slim and light, easy to use and very functional.

What's Not: Takes a while to fully charge.

Reviewed by Tong Zhang

One of the best things about the HTC One is its unibody design that gives the smartphone a modern look. But the design also means you have a non-user replaceable battery. Mophie has released a Juice Pack external battery case that can potentially double the runtime of the HTC One's built-in battery, and unlike some previous juick pack battery cases we've seen, this one is very slim and weighs only 3.7 ounces. The Mophie Juice Pack for HTC One comes in black and silver to match the smartphone's colors.

Design

By now we're all familiar with Mophie's juice pack line of battery cases. The Mophie Juice Pack for HTC One is no exception. The battery case has lithium polymer rechargeable battery built into the case that comes in two parts with a charging connector at the bottom. The case is easy to install: just take the top cap off and slide your phone into the case and then slide the top cap back on. Getting the phone out takes some pulling but it's not too bad either. The battery case is very easy to use thanks to the four white LEDs on the back that indicate battery levels when you press on the small button on the left of the LED lights, and the standby/charge slider on the right of the LEDs. To conserve the battery power in the case and prevent consistent power trickling to your phone, use the slider to charge when you need to charge your phone's battery and put it in standby when your phone doesn't need charging.

The Mophie Juice Pack for HTC One has soft touch coating that feels nice in hand and won't mar or scratch the HTC One when you're handling it with the battery case. The surface is matte but it does show some finger grease. You can clean it with a damp towel. The Mophie Juice Pack for HTC One comes in black and silver. The battery case measures in at 2.88 x 6.06 x 0.67 inches and does add some length to the phone. Unlike some previous juice pack cases, this one is slim and light.

Features

The Mophie Juice Pack for HTC One has a built-in rechargeable battery that's 2500mAh in capacity. The capacity is slightly higher than the built-in battery on the phone and can provide up to a full 100% charge. In our tests, while the phone was idle during the charge, we got about 90% charge from the fully powered battery case and it took about 3 hours to charge. The last 20% battery on the HTC One takes more power and usually longer to fill even with the included charger. Mophie suggests that you start charging your HTC One when it reaches 20% mark when the battery meter turns red on the phone, and stop at 80% to conserves the battery power on the case. Since the Juice Pack counts only full charging cycles, this suggestion makes a lot of sense.

You can charge the Mophie Juice Pack for HTC One with the included USB cable with or without the phone in the case. The charging port on the mophie supports power pass through as well as data pass through. This means when you plug in the Mophie Juice Pack with the phone in it, both the phone and the case will get charge simultaneously and your HTC One can also sync with your computer. The battery case itself takes a few hours to fully charge via USB and is rechargeable for 500 full cycles. After 500 full cycle charges, it'll provide less than 75% of its original capacity. The Mophie Juice Pack for HTC One passes safety tests and won't short circuit your phone or damage its battery.

The Mophie Juice Pack for HTC One is also a very functional case in addition to the added battery power. The case has a generous cutout for the rear camera/flash cluster and perfectly aligned cutouts for the top 3.5mm audio jack and the rear mic. The case has a piece of translucent plastic cover over the power button that doubles as IR port. The volume buttons work well under the case's cover. Luckily the HTC One has dual speakers in the front, and the mophie juice pack case doesn't block anything in the front of the phone. The case does however create a barrier for the front glass so that it doesn't touch any surface when you put the phone face down.

Conclusion

Though the Mophie Juice Pack for HTC One adds some length to an already long phone, it's very slim and light considering what it provides: a lot of extra power and protection for the phone from scratches, bumps and even drops. The battery case is super easy to use and offers access to all buttons and ports. The case supports both power and data pass through, so if you need to use the phone with audio accessories you can use it while it's in the mophie juice pack. We like that the battery case comes in matching colors with the HTC One.